How to add an action to a material?
I am not sure about material action support in unity, however I am pretty sure you can use a UV animation,

Just move the lights face to a copy of the face lit up?

http://answers.unity3d.com/questions/19848/making-textures-scroll-animate-textures.html

This way you just need the 'lit up' texture face in the uv sheet for each color.